1. Field of the Invention
The present invention relates to an intercommunication system for use in an emergency in an elevator in a multiple dwelling house, etc.
2. Description of the Related Art
FIG. 2 is a block diagram showing a conventional emergency intercommunication system for an elevator disclosed in, for example, Japanese Patent Laid-Open No. 240278/1987. In the conventional emergency intercommunication system, a local interphone unit 1 installed in an elevator car is connected, via an adapter 3, with a central interphone unit 2 provided in a control room of the dwelling house, the central interphone unit 2 being also connected with another central interphone unit 2a provided in a machine room. Both the local interphone unit 1 (hereinafter referred to as "the local unit") and the central interphone unit 2 (hereinafter referred to as "the central unit") are connected, via the adapter 3, with an emergency call apparatus 4 which is in turn connected, via a telephone line L, with a general control center 5 where 24-hour control of the dwelling house is performed.
The adapter 3 includes a calling operation detecting section 6 for detecting the operation of a push button (not shown) provided as a calling operation portion of the local unit 1, and a delay timer 7 electrically connected to the detecting section 6. The adapter 3 also includes a bilateral amplifier 8, a switch 9 for selectively connecting the local unit 1 with either the central unit 2 or the bilateral amplifier 8, and a relay 10 for actuating the switch 9.
When the conventional emergency intercommunication system is in its normal operation state, the switch 9 connects the local unit 1 with the central unit 2, and the bilateral amplifier 8 performs amplification only in the direction heading from the emergency call apparatus 4 to the switch 9.
Therefore, in the normal operation state of the system, when the push button of the local unit 1 is depressed, a person in the car, or the calling-out party, can intercommunicate with a person operating the central unit 2 or 2a.
On the other hand, when the calling-out party continues depressing the push button of the local unit 1 while no one is stationed in the control room because, for instance, it is nighttime, this operation of the pushing button is detected by the calling operation detecting section 6. The delay timer 7 detects that the push button is depressed over a predetermined period of time, then sends an actuation signal to the emergency call apparatus 4, thereby actuating the apparatus 4. Upon actuation, the emergency call apparatus 4 sends a circuit closing signal to the adapter 3 via a wire W5, whereby the relay 10 is operated to switch the connection at the switch 9 to the bilateral amplifier 8. This switching causes the local unit 1 to be connected with the bilateral amplifier 8, so that the calling-out party can hear a signal (a dial tone, a selection signal, or a ringing tone) transmitted from the emergency call apparatus 4 via a wire W3. At this time, the bilateral amplifier 8 is still in its unilateral state and is not able to send any audio information from the local unit 1 to the control center 5 which must receive the call from the unit 1.
Subsequently, the actuated emergency call apparatus 4 automatically dials the telephone number of the control center 5 which has previously been stored, to call the control center 5. When the call is received by the control center 5, the emergency call apparatus 4 sends a previously recorded message to the local unit 1 via the wire W3. Thereafter, the apparatus 4 sends a message completion signal to the bilateral amplifier 8 via a wire W4. Upon inputting the message completion signal, the bilateral amplifier 8 is shifted from its unilateral state to its bilateral state, thereby enabling intercommunication between the local unit 1 and the control center 5 via the wire W3.
Thereafter, when the intercommunication line is disconnected by the control center 5 or when a predetermined time has passed since the start of the intercommunication, the emergency call apparatus 4 opens the telephone line L, and, simultaneously, stops sending the circuit closing signal and the message completion signal. Then, the apparatus 4 stands by until there is another emergency call.
When a person takes an elevator in a multiple dwelling house during the nighttime, the user is generally afraid not only because there might be an elevator accident but also because the elevator might be the scene of a crime. For this reason, some measures must be taken to prevent such crimes. However, with the conventional intercommunication system, in order to intercommunicate with the control center 5, one has to continue depressing the push button of the local unit 1 installed in the car for a period at least equal to the time previously set in the timer 7. In an emergency, one may not be able to intercommunicate with the control center 5 before it is too late. Although the user could intercommunicate with the control center 5, it may be difficult to promptly take some action in an emergency since the elevator car is physically separated from the control center 5. Therefore, no effective prevention of crimes can be expected in the conventional system.
This problem may be overcome by installing in the car a telephone which can be directly connected with the control center 5 or the like so that intercommunication with the control center 5, etc. is possible at any time. However, installing such telephones anew in the existing elevators is not easy from the viewpoint of the installation work required.